1. Field of the Invention
The present invention relates to a method for producing porous microneedles.
2. Description of Related Art
The concept of administering medications, that is, medicinal and biochemical active substances, is being pursued in many variants. There are basically several important criteria which have to be observed in this context. Among others of these important criteria are the mechanical stability and the biocompatibility of the microneedles. At the same time, the production of the microneedles should be based on simple and well-controlled processes, in order to work cost-effectively, particularly at high volume.
Porous silicon is regarded as suitable material that basically satisfies the requirements mentioned. The material demonstrates good compatibility with biochemical substances, and is well able to be removed by the human (or animal) body.
Thus, microneedles are known from U.S. Pat. No. 6,334,856, for example, which, besides metals, ceramics and polymers also include porous silicon. There are basically two procedures for producing microneedles from porous silicon: Either (a) a silicon substrate is first made porous, and microneedles are subsequently patterned from this by etching, or (b) the substrate is first etched for the formation of microneedles and porosified thereafter. For reasons of process technology, the first procedure is very difficult. Although it is basically suitable for producing porous microneedles, the second procedure (b) requires a production method having specific step sequences, each individual step having a need to be composed of a well manageable individual process, and all the step sequences together should form an advantageous combination of an overall method. In particular, the method should make possible the production of microneedles without a great technical effort, and thereby in a cost-effective manner. Nevertheless, sufficient mechanical stability of the microneedles thus produced has to be ensured. The microneedles produced therefore must have neither brittle nor soft materials, which could, for instance, lead to splinters chipping off.